Teammate player B, must also be from 98-99?
Can be from any season?
Or can be from any season he was a teammate of player X?

Yes to the last question. You can draft any teammate of a drafted player during a season in which they played together.
So, if I draft Jordan and use 88-89, than Jordan's teammate from his Wizards teams are eligible to be drafted. Or any teammate he played with while with the Bulls, assuming no one else drafts them. However, if for some reason Dennis Rodman went undrafted, than Rodman's seasons with the Pistons or the Spurs would not be eligible, only his seasons with the Bulls.
Does that help?